function [ x0,y0 x0_,y0_ ] = hwozd_getMassCenter( I )
im = double(I.image);
d = size(im);
x0_ = I.x0(round(d(1)/2),round(d(2)/2));
y0_ = I.y0(round(d(1)/2),round(d(2)/2));

x0 = round(  (1 + x0_)/ (2/(d(1)-1))  );
y0 = round(  (1 + y0_)/ (2/(d(2)-1))  );

x0int = I.x0int;
y0int = I.y0int;
%x0 = I.x0int;
%y0 = I.y0int;